1. Field of the Invention
The present invention relates to an operating system of a liquefied natural gas ship for sub-cooling and liquefying boil-off gas, and more particularly, to an operating system of a liquefied natural gas ship for sub-cooling and liquefying boil-off gas in which a re-liquefaction system of boil-off gas in a liquefied natural gas ship is modified into an efficient sub-cooling and liquefaction structure so that power consumption is reduced, operation is simply performed, and economic efficiency can be achieved.
2. Description of the Related Art
Generally, boil-off gas generated from a cargo tank is re-liquefied into liquefied natural gas using a re-liquefaction system installed in a compressor and motor room of a liquefied natural gas ship, and the re-liquefied boil-off gas is returned back to the cargo tank.
There are several basic operating systems in the re-liquefaction system, such as partial liquefaction, saturated liquefaction, sub-cooled liquefaction, and the like. The sub-cooled liquefaction is superior to the others in view of power consumption, simple operation, etc., and the present invention provides an operating system for sub-cooled liquefaction of boil-off gas adapted to have a more efficient structure.